[TrimmableTypeMap] Preserve trimmable typemap outputs on no-op builds

[simonrozsival]

Summary

• Add a new _RecordTrimmableTypeMapFileWrites target that re-emits the trimmable typemap's dynamic outputs (generated typemap DLLs, Java sources, copied android/src/** files, acw-map.txt, AndroidManifest.xml, ApplicationRegistration.java, and the typemap assemblies list) into @(FileWrites) on no-op builds.
• Hook the new target into the public $(IncrementalCleanDependsOn) extension point so MSBuild''s IncrementalClean sees the prior outputs and does not treat them as orphaned when _GenerateJavaStubs / _GenerateTrimmableTypeMap are skipped.
• Refactor the _GeneratedTypeMapAssembliesFromList fan-out in _AddTrimmableTypeMapAssembliesToResolvedAssemblies to populate a single _TrimmableTypeMapResolvedAssemblies item group and include it in both _ResolvedAssemblies and _ShrunkAssemblies, keeping metadata in sync.
• Extend Build_WithTrimmableTypeMap_IncrementalBuild to assert that at least one typemap DLL is produced on the first build and that every generated typemap DLL still exists after the no-op second build.

Related to #10958.

Relevant sub-issues:

• Related to [TrimmableTypeMap] Fix stale per-assembly typemap output invalidation #11489: fixes one incremental-output preservation case, but does not fully address stale per-assembly typemap invalidation from non-assembly input changes.
• Context for [TrimmableTypeMap] Add ComputeTypeMapDependencies pre-task for partial builds #11492 and [TrimmableTypeMap] Split Debug typemap generation into per-assembly MSBuild units #11494: dynamic typemap outputs must remain visible to MSBuild''s incremental clean before deeper partial-build / per-assembly target work.
• Tangentially related to [TrimmableTypeMap] Reconcile ACW map generation with per-assembly incrementality #11495: keeps acw-map.txt recorded in @(FileWrites), but does not split or merge ACW maps.

Validation

• ./dotnet-local.sh build src/Xamarin.Android.Build.Tasks/Tests/Xamarin.Android.Build.Tests/Xamarin.Android.Build.Tests.csproj -p:Configuration=Debug -v:minimal
• ANDROID_SERIAL=emulator-5554 ./dotnet-local.sh test bin/TestDebug/net10.0/Xamarin.Android.Build.Tests.dll --filter "Name=Build_WithTrimmableTypeMap_IncrementalBuild" --logger "console;verbosity=detailed" (test run succeeded; selected cases skipped/inconclusive locally because commercial build targets are unavailable; False,NativeAOT is an unsupported configuration)

[Copilot]

Pull request overview

This PR addresses a trimmable typemap incremental-build issue where MSBuild’s IncrementalClean could delete previously generated typemap DLLs / Java outputs on no-op builds (because skipped targets don’t re-populate @(FileWrites)). It replays the prior dynamic outputs into @(FileWrites) early in the build and strengthens the incremental test to ensure the generated typemap assemblies survive a no-op rebuild.

Changes:

• Add a _RecordTrimmableTypeMapFileWrites target that re-emits typemap-generated DLL/Java outputs into @(FileWrites) before _CleanGetCurrentAndPriorFileWrites runs.
• Refactor typemap assembly item construction via a dedicated @(_TrimmableTypeMapResolvedAssemblies) item list and then feed it into both @(_ResolvedAssemblies) and @(_ShrunkAssemblies).
• Extend Build_WithTrimmableTypeMap_IncrementalBuild to assert typemap DLLs from the first build still exist after a no-op second build.

Reviewed changes

Copilot reviewed 2 out of 2 changed files in this pull request and generated no comments.

File	Description
src/Xamarin.Android.Build.Tasks/Tests/Xamarin.Android.Build.Tests/TrimmableTypeMapBuildTests.cs	Adds an assertion that typemap DLL outputs persist across a no-op rebuild where _GenerateJavaStubs is skipped.
src/Xamarin.Android.Build.Tasks/Microsoft.Android.Sdk/targets/Microsoft.Android.Sdk.TypeMap.Trimmable.targets	Replays prior dynamic typemap outputs into @(FileWrites) before IncrementalClean and slightly restructures typemap DLL item population for packaging/native config.

[simonrozsival]

/review

[github-actions]

✅ Android PR Reviewer completed successfully!

[github-actions]

✅ LGTM — Clean, well-designed incremental build fix

Summary: This PR correctly solves the problem of IncrementalClean deleting dynamically-generated typemap outputs on no-op builds by replaying them into @(FileWrites) via the public $(IncrementalCleanDependsOn) hook. The approach is sound and follows MSBuild best practices.

What's good:

• The _RecordTrimmableTypeMapFileWrites target is well-placed via IncrementalCleanDependsOn — the right hook for this problem
• Excellent comment block explaining why the target exists
• The _TrimmableTypeMapResolvedAssemblies refactoring eliminates metadata duplication cleanly
• Test coverage directly validates the fix scenario

Minor suggestions posted inline (2 💡):

1. Redundant stamp file FileWrites entry (already handled by _AddFilesToFileWrites glob)
2. Missing Assert.IsNotEmpty guard on typemapDlls in the test

⚠️ CI: Could not check CI status (gh is not authenticated in this environment). Please verify CI is green before merging.

Generated by Android PR Reviewer for issue #11472 · ● 13.2M

[simonrozsival]

@copilot address review comments

• _AddFilesToFileWrites (in Xamarin.Android.Common.targets:2663) already adds $(_AndroidStampDirectory)*.stamp via a glob, so this line is a no-op. Removing it would reduce noise and avoid confusion about whether stamps need explicit registration.
• f Directory.GetFiles returns an empty array (e.g., due to a test infrastructure issue or path change), the foreach loop below silently passes without verifying anything. Adding Assert.IsNotEmpty (typemapDlls) here would catch that case and make the test more robust.

[Copilot]

@copilot address review comments

• _AddFilesToFileWrites (in Xamarin.Android.Common.targets:2663) already adds $(_AndroidStampDirectory)*.stamp via a glob, so this line is a no-op. Removing it would ...

Done in 01cf0d5:

• Removed the $(_AndroidStampDirectory)_GenerateJavaStubs.stamp line from _RecordTrimmableTypeMapFileWrites — it's already covered by the *.stamp glob in _AddFilesToFileWrites.
• Added Assert.IsNotEmpty(typemapDlls, ...) immediately after Directory.GetFiles to catch the empty-array case before the foreach.